1H-Imidazo [1&#39;,2&#39;:1,2]pyrrolo[3,4-b]pyridines and their use as herbicidal agents

ABSTRACT

Novel pyridine compounds of formula I below have good selective herbicidal properties pre- and postemergence and also influence or inhibit plant growth. The compounds are of formula I ##STR1## wherein each of X, Y and Z independently of one another is hydrogen or a C 1  -C 4  alkyl group, or two adjacent substituents together also form a saturated or unsaturated 3- or 4-membered alkylene chain or alkenyl chain, each of which chains may in turn by substituted by one to four C 1  -C 4  alkyl groups, R is the hydroxyamino group, a C 1  -C 4  alkoxyamino, C 3  -C 4  alkenyloxyamino or C 3  -C 4  alkynyloxyamino group, a --PO(C 1  -C 4  alkyl) 2  or --PO(CH 3 )OC 1  -C 4  alkyl radical or an unsubstituted or substituted hydrazino radical.

CROSS REFERENCE

This application is a continuation-in-part of the parent applicationSer. No. 837,977 filed Mar. 10, 1986, still pending.

The present invention relates to novel pyridine compounds withherbicidal and plant growth regulating properties, as well as to thepreparation of these novel compounds. The invention also relates tocompositions containing the novel imidazolidinone compounds, and tomethods of using them for selectively controlling weeds or forregulating plant growth.

From the European patent application EP-A 133 309 it is known that1H-imidazo[1',2':1,2]pyrrolo[3,4-b]pyridine-2,5(3H,9bH)-diones which aresubstituted in 9b position inter alia with an amino group areherbicides.

It has now been found, that3-Isopropyl-3-methyl-1H-imidazo-[1',2':1,2]pyrrolo[3,4-b]pyridine-2,5(3H,9bH)-dionesof general formula I which are substituted in position 9b byhydroxylamino, hydrazino or phosphono group (and in which said groupsmight be further substituted as outlined below) show superior herbicidalactivity and selectivity. The new compounds show plant growth regulatingactivities too.

Specifically, the novel pyridine compounds are derivatives of3-isopropyl-3-methyl-1H-imidazo[1',2':1,2]pyrrolo[3,4-b]pyridine-2,5(3H,9bH)-dione,said novel pyridine compounds being of formula I ##STR2## wherein eachof X, Y and Z independently of one another is hydrogen or a C₁ -C₄ alkylgroup, or two adjacent substituents together also form a saturated orunsaturated 3- or 4-membered alkylene chain or alkenylene chain, each ofwhich chains may in turn be substituted by one to four C₁ -C₄ alkylgroups; R is the hydroxyamino group, a C₁ -C₄ alkoxyamino, C₃ -C₄alkenyloxyamino or C₃ -C₄ alkynyloxyamino group, a --PO(OC₁ -C₄ alkyl)₂or --PO(CH₃)OC₁ -C₄ alkyl radical or a hydrazino radical --NR₁ NR₂ R₃,in which R₁ is hydrogen or C₁ -C₄ alkyl, R₂ is hydrogen, C₁ -C₄ alkyl orbenzyl and R₃ is hydrogen, C₁ -C₄ alkyl, benzoyl, carbamoyl,thiobenzoyl, thiocarbamoyl, C₁ -C₄ alkylcarbamoyl, di(C₁ -C₄alkyl)carbamoyl, C₁ -C₄ alkylthiocarbamoyl, di(C₁ -C₄alkyl)-thiocarbamoyl, anilido, thioanilido, C₁ -C₄ alkoxycarbonyl, C₁-C₄ -alkylcarbonyl, C₁ -C₄ alkylthiocarbonyl or benzoyloxy, the phenylrings being unsubstituted or substituted by halogen, C₁ -C₄ alkyl, C₁-C₄ haloalkyl or C₁ -C₄ alkoxy, or R₃ is another3H-imidazol[1',2':1,2]pyrrolo[3,4-b]pyridine-2,5-dion-12-yl radical or athiazolylcarbamoyl radical.

In the above definitions, the alkyl, alkenyl and alkynyl groups may bestraight chain or branched. Examples of such groups are: methyl, ethyl,ethylene, propyl, propylene, isopropyl, 1- or 2-methyl-ethylene, butyl,butylene, sec-butyl, 1-methylpropylene, isobutyl, 2-methylpropylene,tert-butyl, 2,2-dimethylethylene, 1,2-dimethylethylene, allyl,methallyl, butenyl, propargyl, 2-methylpropynyl and butynyl.

Halogen is fluorine, chlorine, bromine or iodine.

The nomenclature of the imidazo[1',2':1,2]pyrrolo[3,4-b]pyridine systemis taken over from Chemical Abstracts; in this text the ring systems arenamed and numbered as follows:

The basic structure for compounds of formula I is: ##STR3## The basicstructure for compounds of formula IIa ##STR4## and for IIb is: ##STR5##The pyrrolo[3,4-b]pyridine of formula IV and V resp. are named as:##STR6## The preparation of such compounds can be represented by thefollowing scheme: ##STR7## The process of the present invention for thepreparation of the imidazolinone compounds of formula I comprisesreacting a compound of formula IIa or IIb of formula V ##STR8## in whichformulae X, Y and Z are as defined for formula I, in an inert organicsolvent or diluent and in the presence of a base, with a compound offormula III

    HR                                                         (III)

wherein R is as defined for formula I, and isolating the resultantcondensation product from the reaction mixture.

The compounds of formula IIa wherein X, Y and Z are not all hydrogen arenovel and constitute an object of this invention.

In said reaction, the compound of formula III is converted in a suitablesolvent such as dioxane, tetrahydrofuran or acetonitrile with thestarting material of formula IIa or IIb to give the compound of formulaI. The reaction is carried out preferably in a basic reaction-medium, ithowever can also be carried out with an acid catalyst. After dilutionwith water and acidification with acids, the resultant product isprecipitated and isolated by filtration or extraction with a solvent.The compound of formula I can be isolated after the solvent has beenevaporated off. The product is obtained in pure form byrecrystallization or distillation under a high vacuum.

Certain starting materials of formulae IIa and IIb are known and othersmay be prepared by known methods.

A pyridine-2,3-dicarboxylic acid α-isopropyl-α-methylacetonitrile offormula IV required as starting material can be prepared in simplemanner in accordance with the process described in European publishedapplication 161 221 by condensing an unsaturated hydrazone with a2-chloro- or 2-bromo-N(α-isopropyl-α-methylacetonitrile)succinimideaccording to the following scheme ##STR9## In the above formulae each ofR' and R" is hydrogen or C₁ -C₄ alkyl, Hal is chlorine or bromine, andX, Y and Z are as defined for formula I.

The starting material of formula V can also be prepared in accordancewith the process described in European patent application 8581062.5 bycondensing an unsaturated hydrazone withN-(α-isopropyl-α-methylacetonitrile)succinimide. In this reaction, atetrahydropyridine-2,3-dicarboximide is formed which is converted intothe pyridine-2,3-dicarboximide by treatment with silica gel andsubsequent oxidation in air according to the following scheme: ##STR10##In the above formula each of R' and R" is hydrogen or C₁ -C₄ alkyl, andX, Y and Z are as defined for formula I.

If the N-(α-isopropyl-α-methylacetonitrile)-2,3-pyridinecarboximide offormula IV is first treated with concentrated sulfuric acid, hydrolysisof the nitrile group yields theN-(α-isopropyl-α-methylacetimido)-2,3-pyridinecarboximide of formula Vwhich can be condensed under basic conditions to give the3-isopropyl-3-methyl-3H-imidazo[1',2':1,2]pyrrolo[3,4-b]pyridine-2,5-dioneof formula IIa. The pyridinecarboximide of formula V can also beconverted, in the presence of a base such as sodium hydroxide solution,into the 2-(4-isopropyl-4-methyl-5-oxoimidazolidine)nicotinic acidderivative of formula VI which is converted into the starting materialof formula IIb(2-isopropyl-2-methyl-3H-imidazo[1',2':1,2]-pyrrolo[3,4-b]pyridine-3,5-dione)by treatment with a condensing agent in an organic solvent, with theloss of a water molecule. Nicotinic acids of formula VI and their estersas well as the preparation thereof are described e.g. in Europeanpublished application 41 623.

Examples of suitable condensing agents for this cyclisation are a molaramount of a strong acid, e.g. sulfuric acid, or of an anhydride, or awater absorbing reagent such as cyclohexanecarbodiimide, thionylchloride or phosgene in the presence of a small amount ofdimethylformamide. Condensation can also be effected by boiling thereaction mixture in a water separator.

If the reactions can not be carried out at room temperature, then theyare carried out in the temperature range from 0° C. to 200° C., i.e. thereaction mixture is heated--if necessary--to its boiling point andcooled--if necessary--with ice/water or ice/brine.

Suitable bases for these condensation or hydrolysis reactions are inparticular inorganic bases such as sodium hydroxide, sodium carbonate,calcium hydroxide, calcium carbonate, potassium hydroxide, potassiumcarbonate, ammonia and tertiary organic bases such as triethylamine.

Suitable solvents are e.g. polar, aprotic solvents which can be used bythemselves or in mixtures consisting of at least two solvents. Examplesof such solvents are: ethers such as dibutyl ether, tetrahydrofuran,dioxane, methylene glycol, dimethyl ethylene glycol, diethyl diethyleneglycol, dimethyl triethylene glycol, halogenated hydrocarbons such asmethylene chloride, chloroform, 1-2-dichloroethane,1,1,1-trichloroethane, 1,1,2,2-tetrachloroethane, carboxylates andlactones such as ethyl acetate, methyl propionate, ethyl benzoate,2-methoxyethyl acetate, γ-butyrolactone, o-valerolactone andpivalolactone, carboxamides and lactams such as formamide, acetamide,N-methylformamide, N,N-dimethylformamide, N,N-diethylformamide,N,N-dimethylacetamide, N,N-diethylacetamide, γ-butyrolactam,ε-caprolactam, N-methylpyrrolidone, N-acetylpyrroldione,N-methylcaprolactam, tetramethylurea, hexamethylphosphoric triamide,sulfoxides such as dimethyl sulfoxide, sulfones such as dimethylsulfone, diethyl sulfone, trimethylene sulfone, tetramethylene sulfone,trimethylamine, N-methylpyrrolidine, N-methylpiperidine,N-methylmorpholine, substituted benzenes such as chlorobenzene,nitrobenzene, nitrobenzene, and nitriles, e.g. acetonitrile.

Preferred herbicides or plant growth regulators are those derivatives of3-isopropyl-3-methyl-1H-imidazo[1',2':1,2]pyrrolo[3,4-b]pyridine-2,5(3H,9bH)-dioneof formula I wherein

R is a hydrazino radical, in particular9b-hydrazino-3,7-dimethyl-3-isopropyl-1H-imidazo[1',2':1,2]pyrrolo[3,4b]pyridine-2,5(3H,9bH)-dione;

R is the hydroxylamino radical, in particular9b-hydroxylamino-3-isopropyl-3-methyl-1H-imidazo[1',2':1,2]pyrrolo[3,4-b]pyridine-2,5(3H,9bH)-dione;

R is a C₁ -C₄ alkoxyamino or C₃ -C₄ alkenyloxyamino radical, inparticular9b-(allyloxyamino)-7-n-butyl-3-isopropyl-3-methyl-1H-imidazo[1',2':1,2]-pyrrolo[3,4-b]pyridine-2,5(3H,9bH)-dione,especially3-isopropyl-9b-methoxyamino-3-methyl-1H-imidazo[1',2':1,2]pyrrolo[3,4-b]pyridin-2,5(3H,9bH)-dione

9b-allyloxyamino-3-isopropyl-3-methyl-1H-imidazo[1',2':1,2]pyrrolo[3,4-b]pyridine-2,5(3H,9bH)-dioneand

7-ethyl-9b-allyloxyamino-3-isopropyl-1H-imidazo[1',2':1,2]pyrrolo[3,4b]pyridine-2,5(3H,9bH)-dione;

The invention relates to all diastereomeric and enantiomeric isomers ofthe compounds of formula I.

The compounds of formula I are usually successfully applied atconcentrations of 0.05 to 4 kg/ha, in particular 0.1 to 1 kg/ha.

When used at low rates of application, the compounds of formula I havegood selective growth inhibiting and selective herbicidal propertieswhich make them most suitable for use in crops of useful plants,preferably in cereals, cotton, soybeans, maize and rice. In some casesdamage is also caused to weeds which have only been controlled up to nowwith total herbicides.

The mode of action of these compounds is unusual. Many aretranslocatable, i.e. they are absorbed by the plant and transported toother parts of it where they then exert their action. Thus, for example,it is possible, to damage perennial weeds to the roots by surfacetreatment. Compared with other herbicides and growth regulators, thenovel compounds of formula I are effective even when used at very lowrates of application.

The compounds of formula I have in addition pronounced growthregulating, especially growth inhibiting, properties. The growth of bothmonocots and dicots is inhibited.

Thus, for example, the compounds of formula I selectively inhibit thegrowth of leguminosae which are frequently planted as cover crops intropical regions, so that, while soil erosion between cultivated plantsis prevented, the cover crops cannot compete with the cultivated plants.

Inhibition of the vegetative growth of many cultivated plants permitsmore plants to be sown in a crop area, so that a higher yield may beobtained per unit of area. A further mechanism of yield increase usinggrowth regulators resides in the fact that nutrients are ableincreasingly to promote flower formation and fruiting, whereasvegetative growth is inhibited.

At higher rates of application of compounds of formula I, all testedplants are so severely damaged in their development that they die.

The invention also relates to herbicidal and growth regulatingcompositions which contain a novel compound of formula I, and also tomethods of controlling weeds pre- and postemergence and of inhibitingthe growth of monocots and dicots, especially grasses, tropical covercrops and tobacco plant suckers.

The compounds of formula I are used in unmodified form or, preferably,together with the adjuvants conventionally employed in the art offormulation, and are therefore formulated in known manner toemulsifiable concentrates, directly sprayable or dilutable solutions,dilute emulsions, wettable powders, soluble powders, dusts, granulates,and also encapsulations in e.g. polymer substances. As with the natureof the compositions, the methods of applications, such as spraying,atomising, dusting, scattering or pouring, are chosen in accordance withthe intended objectives and the prevailing circumstances.

The formulations, i.e. the compositions, preparations or mixturescontaining the compound (active ingredient) of formula I and, whereappropriate, a solid or liquid adjuvant, are prepared in known manner,e.g. by homogeneously mixing and/or grinding the active ingredients withextenders, e.g. solvents, solid carriers and, where appropriate,surface-active compounds (surfactants).

Suitable solvents are: aromatic hydrocarbons, preferably the fractionscontaining 8 to 12 carbon atoms, e.g. xylene mixtures or substitutednaphthalenes, phthalates such as dibutyl phthalate or dioctyl phthalate,aliphatic hydrocarbons such as cyclohexane or paraffins, alcohols andglycols and their ethers and esters, such as ethanol, ethylene glycol,ethylene glycol monomethyl or monoethyl ether, ketones such ascyclohexanone, strongly polar solvents such as N-methyl-2-pyrrolidone,dimethyl sulfoxide or dimethylformamide, as well as vegetable oils orepoxidised vegetable oils such as epoxidised coconut oil or soybean oil;or water.

The solid carriers used e.g. for dusts and dispersible powders arenormally natural mineral fillers such as calcite, talcum, kaolin,montmorillonite or attapulgite. In order to improve the physicalproperties it is also possible to add highly dispersed silicic acid orhighly dispersed absorbent polymers. Suitable granulated adsorptivecarriers are porous types, for example pumice, broken brick, sepioliteor bentonite; and suitable nonsorbent carriers are materials such ascalcite or sand. In addition, a great number of pregranulated materialsof inorganic or organic nature can be used, e.g. especially dolomite orpulverised plant residues.

Depending on the nature of the compound of formula I to be formulated,suitable surface-active compounds are nonionic, cationic and/or anionicsurfactants having good emulsifying, dispersing and wetting properties.The term "surfactants" will also be understood as comprising mixtures ofsurfactants.

Suitable anionic surfactants can be both water-soluble soaps andwater-soluble synthetic surface-active compounds.

Suitable soaps are the alkali metal salts, alkaline earth metal salts orunsubstituted or substituted ammonium salts of higher fatty acids (C₁₀-C₂₂), e.g. the sodium or potassium salts of oleic or stearic acid, orof natural fatty acid mixtures which can be obtained e.g. from coconutoil or tallow oil. Mention may also be made of fatty acid methyltaurinsalts.

More frequently, however, so-called synthetic surfactants are used,especially fatty sulfonates, fatty sulfates, sulfonated benzimidazolederivatives or alkylarylsulfonates.

The fatty sulfonates or sulfates are usually in the form of alkali metalsalts, alkaline earth metal salts or unsubstituted or substitutedammonium salts and contain a C₈ -C₂₂ alkyl radical which also includesthe alkyl moiety of acyl radicals, e.g. the sodium or calcium salt oflignosulfonic acid, of dodecylsulfate or of a mixture of fatty alcoholsulfates obtained from natural fatty acids. These compounds alsocomprise the salts of sulfuric acid esters and sulfonic acids of fattyalcohol/ethylene oxide adducts. The sulfonated benzimidazole derivativespreferably contain 2 sulfonic acid groups and one fatty acid radicalcontaining 8 to 22 carbon atoms. Examples of alkylarylsulfonates are thesodium, calcium or triethanolamine ethanolamine salts ofdodecylbenzenesulfonic acid, dibutylnaphthalenesulfonic acid, or of anaphthalenesulfonic acid/formaldehyde condensation product.

Also suitable are corresponding phosphates, e.g,. salts of thephosphoric acid ester of an adduct of p-nonylphenol with 4 to 14 molesof ethylene oxide, or phospholipids.

Non-ionic surfactants are preferably polyglycol ether derivatives ofaliphatic or cycloaliphatic alcohols, or saturated or unsaturated fattyacids and alkylphenols, said derivatives containing 3 to 10 glycol ethergroups and 8 to 20 carbon atoms in the (aliphatic) hydrocarbon moietyand 6 to 18 carbon atoms in the alkyl moiety of the alkylphenols.

Further suitable non-ionic surfactants are the water-soluble adducts ofpolyethylene oxide with polypropylene glycol,ethylenediaminopolypropylene glycol and alkylpolypropylene glycolcontaining 1 to 10 carbon atoms in the alkyl chain, which adductscontain 20 to 250 ethylene glycol ether groups and 10 to 100 propyleneglycol ether groups. These compounds usually contain 1 to 5 ethyleneglycol units per propylene glycol unit.

Representative examples of non-ionic surfactants arenonylphenolpolyethoxyethanols, castor oil polyglycol ethers,polypropylene/polyethylene oxide adducts,tributylphenoxypolyethoxyethanol, polyethylene glycol andoctylphenoxypolyethoxyethanol.

Fatty acid esters of polyoxyethylene sorbitate, such as polyoxyethylenesorbitan trioleate, are also suitable non-ionic surfactants. Cationicsurfactants are preferably quaternary ammonium salts which contain, asN-substituent, at least one C₈ -C₂₂ alkyl radical and, as furthersubstituents, unsubstituted or halogenated lower alkyl, benzyl orhydroxy-lower alkyl radicals. The salts are preferably in the form ofhalides, methylsulfates or ethylsulfates, e.g. stearyltrimethylammoniumchloride or benzyldi(2-chloroethyl)ethylammonium bromide.

The surfactants customarily employed in the art of formulation aredescribed e.g in the following publications:

"McCutcheon's Detergents and Emulsifiers Annual", MC Publishing Corp.,Ridgewood, N.J., 1981; H. Stache, "Tensid-Taschenbuch" (Handbook ofSurfactants), C. Hanser Verlag, Munich & Vienna, 1981.

The compositions usually contain 0.1 to 95%, preferably 0.1 to 80%, of acompound of formula I, 1 to 99.9% of a solid or liquid adjuvant, and 0to 25%, preferably 0.1 to 25%, of a surfactant.

Preferred formulations are composed in particular of the followingconstituents (%=percentage by weight):

    ______________________________________                                        Emulsifiable concentrates                                                     compound of formula I:                                                                       1 to 20%,  preferably 5 to 10%                                 surfactant:    5 to 30%,  preferably 10 to 20%                                liquid carrier:                                                                              50 to 94%, preferably 70 to 85%                                Dusts                                                                         compound of formula I:                                                                       0.1 to 10%,                                                                              preferably 0.1 to 1%                                solid carrier: 99.9 to 90%,                                                                             preferably 99.9 to 99%                              Suspension concentrates                                                       compound of formula I:                                                                       5 to 75%,  preferably 10 to 50%                                water:         94 to 25%, preferably 90 to 30%                                surfactant:    1 to 40%,  preferably 2 to 30%                                 Wettable powders                                                              compound of formula I:                                                                       0.5 to 90%,                                                                              preferably 1 to 80%                                 surfactant:    0.5 to 20%,                                                                              preferably 1 to 15%                                 solid carrier: 5 to 95%,  preferably 15 to 90%                                Granulates                                                                    compound of formula I:                                                                       0.5 to 30%,                                                                              preferably 3 to 15%                                 solid carrier: 99.5 to 70%,                                                                             preferably 97 to 85%.                               ______________________________________                                    

Whereas commercial products will be preferably formulated asconcentrates, the end user will normally employ dilute formulations. Theformulations can be diluted to a concentration as low as 0.001% ofactive ingredient. The rates of application are usually from 0.005 to 5kg a.i./ha.

The compositions may also contain further ingredients such asstabilisers, antifoams, viscosity regulators, binders, tackifiers, aswell as fertilisers and other compounds for obtaining special effects.

EXAMPLE 1 Preparation of3-isopropyl-3-methyl-7-n-propyl-3H-imidazo[1',2':1,2]pyrrolo[3,4-b]pyridine-2,5-dione(starting material) ##STR11## With the simultaneous addition of 0.5 g ofpowdered sodium hydroxide, a solution ofα-[3-n-propyl-6H-pyrrolo[3,4-b]pyridine-5,7-dione-6-yl]-α-isopropyl-α-methyl-acetamide(m.p.: 82° C.) in 100 ml of toluene is heated under reflux for 2 hoursin a water separator. After the reaction solution has cooled, it isfiltered through silica gel and the filtrate is washed with ethylacetate and then concentrated by evaporation. The residue isrecrystallised from ethyl acetate/petroleum ether, affording 13.1 g ofthe title compound which melts at 116° C.

The starting materials listed in Table 1 are obtained by following aprocedure analogous to that of Example 1.

                                      TABLE 1                                     __________________________________________________________________________     ##STR12##                           IIa                                      Comp.                                                                             X          Y          Z   phys. data                                      __________________________________________________________________________    1.01                                                                              H          nC.sub.3 H.sub.7                                                                         H   m.p. 116° C.                             1.02                                                                              H          C.sub.2 H.sub.5                                                                          H   m.p. 119-120° C.                         1.03                                                                              H          n-C.sub.4 H.sub.9                                                                        H   m.p. 86-87° C.                           1.04                                                                              H          CH(CH.sub.3).sub.2                                                                       H                                                   1.05                                                                              H          CH.sub.3   H   m.p. 102-106° C.                         1.06                                                                              C.sub.2 H.sub.5                                                                          CH.sub.3   H   m.p. 128-129° C.                         1.07                                                                              (CHCH).sub.2                                                                             --         H                                                   1.08                                                                              H          (CHCH).sub.2                                                                             --                                                  1.09                                                                              H          (CH.sub.2CH.sub.2).sub.2                                                                 --                                                  1.10                                                                              (CH.sub.2CH.sub.2 ).sub.2                                                                --         H   m.p. 95° C.                              1.11                                                                              CH.sub.3   H          CH.sub.3                                            1.12                                                                              H          (CH.sub.2CH.sub.2).sub.2                                                                 --                                                  1.13                                                                              H          H          CH.sub.3                                            1.14                                                                              H          CH.sub.3   CH.sub.3                                            1.15                                                                              H          CH(CH.sub.3)C.sub.2 H.sub.5                                                              H                                                   __________________________________________________________________________

EXAMPLE 2 Preparation of2-isopropyl-2-methyl-7-n-propyl-3H-imidazo[1',2':1,2]pyrrolo[3,4-b]pyridine-3,5-dione(starting material) ##STR13##

With stirring, 15 g (0.05 mole) of2-(5-isopropyl-5-methyl-imidazole-3H-4-one-2-yl)-5n-propylnicotinic acidare added to a solution of 11.1 g of dicyclohexylcarbodiimide in 100 mlof methylene chloride. Stirring is continued for a further 2 hours atroom temperature. The resultant dicyclohexylurea is removed by suctionfiltration and the residue is washed with a small amount of methylenechloride. The filtrate is concentrated by evaporation and the residue isrecrystallised from ethyl acetate/hexane, affording the title product in91% yield (12.1 g) in the form of crystals which melt at 132°-133° C.

The starting materials listed in Table 2 are obtained by following aprocedure analogous to that of Example 2.

                  TABLE 2                                                         ______________________________________                                         ##STR14##                     IIb                                            Comp. X        Y          Z      phys. data                                   ______________________________________                                        2.01  H        n-C.sub.3 H.sub.7                                                                        H      m.p. 132-133° C.                      2.02  H        CH(CH.sub.3).sub.2                                                                       H      m.p. 145-146° C.                      2.03  H        C.sub.2 H.sub.5                                                                          H      m.p. 136-138° C.                      2.04  H        n-C.sub.4 H.sub.9                                                                        H      m.p. 116-119° C.                      2.05  C.sub.2 H.sub.5                                                                        CH.sub.3   H                                                   2.06  (CHCH).sub.2    H                                                       2.07  (CH.sub.2CH.sub.2).sub.2                                                                      H                                                       2.08  H        CH.sub.3   H      m.p. 129-131° C.                      2.09  H        (CHCH).sub.2                                                   2.10  H        (CH.sub.2CH.sub.2).sub.2                                       ______________________________________                                    

EXAMPLE 3 Preparation of11b-hydrazino-3-isopropyl-3-methyl-1H-imidazo[1',2':1,2]pyrrolo[3,4-b]quinoline-2,5(3H,11bH)-dione##STR15## 85 ml of triethylamine and 2.1 g of hydrazine hydrochlorideare added to a mixture of 8.8 g of2-isopropyl-2-methyl-2H-imidazo[1',2':1,2]pyrrolo[3,4-b]quinoline-3,5-dionein 50 ml of tetrahydrofuran, and the batch is stirred for about 30 hoursat room temperature. The solvent is then concentrated by evaporation andthe residue is stirred in 200 ml of water, whereupon the final productcrystallises. The product is isolated by suction filtration and dried.Yield: 6.4 g; m.p. 280°-283° C. EXAMPLE 4 Preparation of3-isopropyl-3-methyl-9b-(N'-methyl-N'-anilinothiocarbonylhydrazino)-1H-imidazo[1',2':1,2]pyrrolo[3,4-b]-pyridine-2,5(3H,9bH)-dione##STR16## With stirring, 5.4 g of 1-amino-1methyl-3-phenylthiourea areslowly added dropwise to a mixture of 7.3 g of2-isopropyl-2-methyl-2H-imidazo[1',2':1,2]pyrrolo[3,4-b]pyridine-3,5-dionein 100 ml of tetrahydrofuran. After everything has been added, stirringis continued for 18 hours at room temperature. The reaction mixture isthen concentrated by evaporation and the residue is recrystallised fromdiethyl ether. Yield: 9 g of the title product; m.p. 162°-163° C.

The compound listed in Table 6 are obtained by following a procedureanalogous to those of Examples 8 and 9.

                                      TABLE 3                                     __________________________________________________________________________     ##STR17##                                                                    Comp.                                                                             X Y        Z R.sub.6            phys. data                                __________________________________________________________________________    3.01                                                                              H H        H NH.sub.2           m.p. 195-225° C.                   3.02                                                                              H H        H NHCOOCH.sub.3      m.p. 112° C.                       3.03                                                                              H H        H                                                                                ##STR18##         m.p. 162-163° C. Example 4         3.04                                                                              H H        H 3-isopropyl-3-methyl-1Himi-                                                                      m.p. 227° C.                                        dazo[1',2':1,2]pyrrolo-                                                                          (decomp.)                                                  [3,4-b]pyridine-2,5(3H,9b)-dion-9b-amino                     3.05                                                                              H H        H 4-methylthiazol-5-ylcarbamoyl                                                                    m.p. 197-198° C.                   3.06                                                                              H CH.sub.3 H NH.sub.2                                                     3.07                                                                              H CH.sub.3 H 3,7-dimethyl-3-isopropyl-1H                                                                      m.p. 207-208° C.                                    imidazo[1',2':1,2]pyrrolo-                                                    [3,4-b]pyridine-2,5(3H,9bH)-dion-9b-amino                    3.08                                                                              H C.sub.2 H.sub.5                                                                        H NH.sub.2                                                     3.09                                                                              H (CH.sub.2CH).sub.2                                                                       NH.sub.2           m.p. 280-283° C.                                                       Example 3                                 3.10                                                                              H (CH.sub.2CH).sub.2                                                                       NHCOOCH.sub.3                                                3.11                                                                              H (CH.sub.2CH).sub.2                                                                       NHCOCH.sub.3                                                 3.12                                                                              H CH.sub.3 H NHCOCH.sub.3                                                 3.13                                                                              H C.sub.2 H.sub.5                                                                        H N(CH.sub.3).sub.2                                            3.14                                                                              H CH.sub.3 H N(CH.sub.3).sub.2                                            __________________________________________________________________________

EXAMPLE 5 Preparation of9b-hydroxylamino-3-isopropyl-3-methyl-3H-imidazo[1',2':1,2]pyrrolo[3,4-b]pyridine-2,5(3H,9bH)-dione##STR19## A mixture of 7.3 g of3-isopropyl-3-methyl-3H-imidazo[1',2':1,2]-pyrrolo[3,4-b]pyridine-2,5-dione,100 ml of acetonitrile, 2.3 g of hydroxylamine hydrochloride and 7 ml oftriethylamine is stirred at room temperature. After about 30 hours, thesolvent is evaporated off under reduced pressure and water and is addedto the residue and, after brief stirring, the analytically pure titleproduct is obtained in crystalline form. Yield after suction filtrationand drying: 5 g; m.p. 163.5°-164.3° C. with decomposition.

The compounds listed in Table 4 are obtained by following a procedureanalogous to that of Example 5.

                  TABLE 4                                                         ______________________________________                                         ##STR20##                                                                    Comp. X           Y            Z    phys. data                                ______________________________________                                        4.01  H           H            H    m.p.                                                                          163-164° C.                                                            (decomp.)                                                                     Example 5                                 4.02  H           CH.sub.3     H    m.p.                                                                          159-161° C.                        4.03  H           C.sub.2 H.sub.5                                                                            H                                              4.04  H           C.sub.3 H.sub.7 n                                                                          H                                              4.05  H           CH(CH.sub.3).sub.2                                                                         H                                              4.06  CH.sub.3    C.sub.4 H.sub.9 n                                                                          H                                              4.07  H           (CHCH).sub.2      m.p. 196° C.                                                           (decomp.)                                 4.08  H           (CH.sub.2CH.sub.2).sub.2                                    4.09  CH.sub.3    H            H                                              4.10  H           CH.sub.3     CH.sub.3                                       4.11  H           C.sub.2 H.sub.5                                                                            CH.sub.3                                       4.12  (CHCH).sub.2             H                                              ______________________________________                                    

EXAMPLE 6 Preparation of9b-allyloxyamino-7-n-butyl-3-isopropyl-3-methyl-1H-imidazo[1',2']pyrrolo[3,4-b]pyridine-2,5(3H,9bH)-dione##STR21## 2.95 ml of triethylamine and 2.3 g of O-allylhydroxylaminehydrochloride are added to a stirred mixture of 5 g of7-n-butyl-3-isopropyl-3-methyl-3H-imidazo[1',2':1,2]pyrrolo[3,4-b]pyridine-2,5-dionein 50 ml of dioxane. The reaction mixture is stirred for several hoursat room temperature, then diluted with about 500 ml of water andextracted with ethyl acetate. The organic phase is dried andconcentrated by evaporation and the residue is recrystallised fromacetone/water, affording in good yield (5.3 g) the title product, whichmelts at 143°-145° C.

The compounds listed in Table 5 are obtained by following a procedureanalogous to those of Example 6 using corresponding starting materials.

                                      TABLE 5                                     __________________________________________________________________________     ##STR22##                                                                    Comp.                                                                             X        Y        Z R.sup.2 phys. data                                    __________________________________________________________________________    5.01                                                                              H        C.sub.2 H.sub.5                                                                        H CH.sub.2 CHCH.sub.2                                                                   m.p. 198-200° C.                       5.02                                                                              H        H        H CH.sub.2 CHCH.sub.2                                                                   m.p. 122-125° C.                       5.03                                                                              H        nC.sub.4 H.sub.9                                                                       H CH.sub.2 CHCH.sub.2                                                                   m.p. 143-145° C.                                                       Example 6                                     5.04                                                                              H        H        H CH.sub.3                                                                              m.p. 191-193° C.                       5.05                                                                              H        CH.sub.3 H CH.sub.3                                              5.06                                                                              H        C.sub.2 H.sub.5                                                                        H CH.sub.3                                                                              m.p. 187-189° C.                                                       (decomp.)                                     5.07                                                                              H        H        H C.sub.2 H.sub.5                                                                       m.p. 135-136° C.                       5.08                                                                              H        H        H C.sub.3 H.sub.7n                                      5.09                                                                              H        H        H C.sub.4 H.sub.9n                                      5.10                                                                              H        C.sub.2 H.sub.5                                                                        H C.sub.2 H.sub.5                                       5.11                                                                              H        CH.sub.3 H CH(CH.sub.3).sub.2                                    5.12                                                                              H        CHCH       CH.sub.3                                              5.13                                                                              (CHCH)            H CH.sub.3                                              5.14                                                                              H        (CHCH).sub.2                                                                             CH.sub.2 CHCH.sub.2                                   5.15                                                                              H        CH.sub.3 H C.sub.2 H.sub.5                                                                       m.p. 192-194° C.                       5.16                                                                              H        H        H 2-chlorobenzyl                                                                        m.p. 193-194° C.                       __________________________________________________________________________

EXAMPLE 7 Preparation of9b-diethylphosphonyl-3-isopropyl-3-methyl-1H-imidazo[1',2':1,2]pyrrolo[3,4-b]pyridine-2,5(3H,9bH)-dione##STR23## A mixture of 6 g of3-isopropyl-3-methyl-3H-imidazo[1',2':1,2]-pyrrolo[3,4-b]pyridine-2,5-dioneand 50 ml of diethyl phosphite is heated for 3 hours to 100° C. andsubsequently concentrated by rotary evaporation. The residue isrecrystallised from acetone and methylene chloride. The yield of titleproduct is 3 g; m.p.: 190°-194° C.

The compounds listed in Table 6 are obtained by following a procedureanalogous to that of Example 7 using corresponding starting materials.

                                      TABLE 6                                     __________________________________________________________________________    Comp.                                                                             X  Y  Z  R.sub.3 R.sub.4  phys. data                                      __________________________________________________________________________    6.01                                                                              H  H  H  OC.sub.2 H.sub.5                                                                      OC.sub.2 H.sub.5                                                                       m.p. 190-194° C.                         6.02                                                                              H  H  H  OCH.sub.3                                                                             OCH.sub.3                                                                              m.p. 140-143° C.                         6.03                                                                              H  H  H  CH.sub.3                                                                              OCH.sub.2 CH(CH.sub.2).sub.2                                                           resin                                           6.04                                                                              H  H  H  OCH(CH.sub.3).sub.2                                                                   OCH(CH.sub.3).sub.2                                                                    m.p. 165-170° C.                                                       (decomp.)                                       6.05                                                                              H  C.sub.2 H.sub.5                                                                  H  OC.sub.2 H.sub.5                                                                      OC.sub.2 H.sub.5                                         6.06                                                                              H  C.sub.2 H.sub.5                                                                  H  OCH.sub.3                                                                             OCH.sub.3                                                6.07                                                                              H  C.sub.2 H.sub.5                                                                  H  OCH(CH.sub.3).sub.2                                                                   OCH(CH.sub.3).sub.2                                      6.08                                                                              H  CH.sub.3                                                                         H  OCH.sub.3                                                                             OCH.sub.3                                                6.09                                                                              H  CH.sub.3                                                                         H  OC.sub.2 H.sub.5                                                                      OC.sub.2 H.sub.5                                         6.10                                                                              H  CH.sub.3                                                                         H  OCH(CH.sub.3).sub.2                                                                   OCH(CH.sub.3).sub.2                                      __________________________________________________________________________

FORMULATION EXAMPLES EXAMPLE 8 Formulation Examples for compounds offormula I (percentages are by weight)

    ______________________________________                                        (a) Wettable powders (a)     (b)     (c)                                      ______________________________________                                        compound of Tables 3 to 6                                                                          20%     60%     0.5%                                     sodium lignosulfonate                                                                              5%      5%      5%                                       sodium laurylsulfate 3%      --      --                                       sodium diisobutylnaphthalenesulfonate                                                              --      6%      6%                                       octylphenol polyethylene glycol ether                                                              --      2%      2%                                       (7-8 moles of ethylene oxide)                                                 highly dispersed silicic acid                                                                      5%      27%     27%                                      kaolin               67%     --      --                                       sodium chloride      --      --      59.5%                                    ______________________________________                                    

The active ingredient is thoroughly mixed with the adjuvants and themixture is thoroughly ground in a suitable mill, affording wettablepowders which can be diluted with water to give suspensions of thedesired concentration.

    ______________________________________                                        (b) Emulsifiable concentrate                                                                         (a)    (b)                                             ______________________________________                                        compound of Tables 3 to 6                                                                            10%    1%                                              octylphenol polyethylene glycol ether                                                                3%     3%                                              (4-5 moles of ethylene oxide)                                                 calcium dodecylbenzenesulfonate                                                                      3%     3%                                              castor oil polyglycol ether                                                                          4%     4%                                              (36 moles of ethylene oxide)                                                  cyclohexanone          30%    10%                                             xylene mixture         50%    79%                                             ______________________________________                                    

Emulsions of any required concentration can be obtained from thisconcentrate by dilution with water.

    ______________________________________                                        (c) Dusts           (a)     (b)                                               ______________________________________                                        compound of Tables 3 to 6                                                                         0.1%    1%                                                talcum              99.9%   --                                                kaolin              --      99%                                               ______________________________________                                    

Dusts which are ready for use are obtained by mixing the activeingredient with the carrier, and grinding the mixture in a suitablemill.

    ______________________________________                                        (d) Extruder granulate                                                                             (a)    (b)                                               ______________________________________                                        compound of Tables 3 to 6                                                                          10%    1%                                                sodium lignosulfonate                                                                              2%     2%                                                carboxymethylcellulose                                                                             1%     1%                                                kaolin               87%    96%                                               ______________________________________                                    

The active ingredient is mixed and ground with the adjuvants, and themixture is subsequently moistened with water. The mixture is extrudedand then dried in a stream of air.

    ______________________________________                                        (e) Coated granulate                                                          ______________________________________                                        compound of Tables 3 to 6 3%                                                  polyethylene glycol (mol. wt. 200)                                                                      2%                                                  kaolin                    94%                                                 ______________________________________                                    

The finely ground active ingredient is uniformly applied, in a mixer, tothe kaolin moistened with polyethylene glycol. Non-dusty coatedgranulates are obtained in this manner.

    ______________________________________                                        (f) Suspension concentrate                                                                            (a)    (b)                                            ______________________________________                                        compound of Tables 3 to 6                                                                             40%    5%                                             ethylene glycol         10%    10%                                            nonylphenol polyethylene glycol ether                                                                 6%     1%                                             (15 moles of ethylene oxide)                                                  sodium lignosulfonate   10%    5%                                             carboxymethylcellulose  1%     1%                                             37% aqueous formaldehyde solution                                                                     0.2%   0.2%                                           silicone oil in the form of a 75%                                                                     0.8%   0.8%                                           aqueous emulsion                                                              water                   32%    77%                                            ______________________________________                                    

The finely ground active ingredient is intimately mixed with theadjuvants, giving a suspension concentrate from which suspensions of anydesired concentration can be obtained by dilution with water.

    ______________________________________                                        (g) Salt solution                                                             ______________________________________                                        compound of Tables 3 to 6  5%                                                 isopropylamine             1%                                                 octylphenol polyethylene glycol ether                                                                    3%                                                 (78 moles of ethylene oxide)                                                  water                      91%                                                ______________________________________                                    

BIOLOGICAL EXAMPLES EXAMPLE 9 Preemergence herbicidal action

In a greenhouse, immediately after sowing the test plants in seeddishes, the surface of the soil is treated with an aqueous dispersion ofthe test compounds, obtained from a 25% emulsifiable concentrate.Concentrations of 4 kg of test compound per hectare are applied. Theseed dishes are kept in the greenhouse at 22°-25° C. and 50% relativehumidity. The test is evaluated 3 weeks later in accordance with thefollowing rating:

1: plant has not germinated or it has dried

2-3: very severe damage

4: severe damage

5: moderate damage, stunted growth

6: damage, the plant can regenerate

7-8: slight damage

9: normal growth, as untreated plants

In this test, the compounds of Tables 3 to 6 exhibit strong herbicidalactivity. A number of results are given in Table 6.

                  TABLE 6                                                         ______________________________________                                        Compound   Avena   Setaria   Sinapsis                                                                             Stellaria                                 ______________________________________                                        5.01       2       1         2      2                                         5.02       2       1         2      2                                         5.03       7       3         3      3                                         ______________________________________                                    

EXAMPLE 10 Postemergence herbicidal action (contact herbicide)

A number of weeds, both mono- and dicotyledonous, are sprayedpostemergence in the 4- to 6-leaf stage with an aqueous activeingredient dispersion at a rage of 4 kg of test compound per hectare andkept at 24°-26° C. and 45-60% relative humidity. The test is evaluated15 days later in accordance with the same rating as employed above. Inthis test, the compounds of Tables 3 to 6 also exhibit strong to verystrong herbicidal activity. A number of results are given in Table 7.

                  TABLE 7                                                         ______________________________________                                        Com-                                                                          pound Avena   Setaria Lolium                                                                              Solanum                                                                              Sinapsis                                                                           Stellaria                             ______________________________________                                        5.01  5       4       4     1      2    2                                     5.02  1       2       2     1      1    2                                     ______________________________________                                    

EXAMPLE 11 Postemergence herbicidal action

The plants tested are treated postemergent with a WP-formulationcontaining 25% of active ingredient and an application rate of 2000,1000, 500, 250 and 125 g AS/ha. The test is evaluated according toexample 10.

The compound tested are of formula I ##STR24##

According to the invention

R=NHOH (Compound 4.01, example 5)

R=NHOCH₃ (Compound 5.04, example 6)

State of the art

R=NH₂ (Compound 2 at page 59 in EP-A 133309)

The following results are obtained:

                                      TABLE 8                                     __________________________________________________________________________             Compound 4.01                                                                           Compound 5.04                                                                           State of the Art                                          (R = NHOH)                                                                              (R = NHOCH.sub.3)                                                                       (R = NH.sub.2)                                   Plants tested                                                                          A B C D E A B C D E A B C D E                                        __________________________________________________________________________    Avena fatua                                                                            2 2 2 2 8 1 1 3 6 8 3 4 5 7 9                                        Digitaria sang.                                                                        1 1 1 2 3 1 2 2 7 7 2 2 3 4 5                                        Xanthium Sp.                                                                           1 1 1 2 2 1 1 2 2 2 1 2 2 2 3                                        Chenopodium Sp.                                                                        1 1 1 1 4 1 1 2 3 6 1 2 2 4 7                                        Solarium nigrum                                                                        1 1 1 2 2 1 1 1 1 1 4 4 4 4 4                                        Sinapis  2 3 3 3 3 1 1 1 2 3 2 3 3 4 4                                        Veronica Sp.                                                                           1 2 2 2 2 1 1 2 2 7 3 3 3 4 5                                        __________________________________________________________________________     legend: Application rate:                                                     A: 2000 g/ha                                                                  B: 1000 g/ha                                                                  C: 500 g/ha                                                                   D: 250 g/ha                                                                   E: 125 g/ha                                                              

It can be seen from table 10 that the compounds according to theinvention show superior activity even at lower application rates.

EXAMPLE 12 Preemergence herbicidal action

Plastic pots are filled with expanded vermiculite (density: 0.135 g/cm³; water-absorbing capacity: 0.565 1/1). After the non-adsorptivevermiculite has been saturated with an aqueous emulsion in deionisedwater which contains the test compound in a concentration of 70.8 ppm,seeds of the following plants are sown on the surface: Nasturtiumofficinalis, Agrostis tenuis, Stellaria media and Digitaria sanguinalis.The pots are then kept in a climatic chamber at 20° C., an illuminationof about 20 klux and a relative humidity of 70%. During the germinatingphase of 4 to 6 days, the pots are covered with lightpermeable materialand watered with deionised water to increase the local humidity. Afterthe 5th day, 0,5% of a commercial liquid fertiliser (Greenzit®) is addedto the water. The test is evaluated 12 days after sowing and the actionon the plants is assessed in accordance with the rating indicated inExample 9.

The results are given in Table 9:

                  TABLE 9                                                         ______________________________________                                              Rate of                                                                       applica- Nasturtium                                                                              Agrostis                                                                             Stellaria                                                                             Digitaria                             Comp. tion ppm officinalis                                                                             tenuis media   sang.                                 ______________________________________                                        5.01           2         2      2       2                                     5.02  100      2         2      2       2                                            10      3         3      4       4                                     5.03  100      2         2      2       2                                            10      3         4      7       7                                     ______________________________________                                    

EXAMPLE 13 Herbicidal action in wild rice (paddy)

The weeds Echinocloa crus galli and Monocharia vag., which occur inwater, are sown in plastic beakers (surface: 60 cm² ; volume: 500 ml).After sowing, the beakers are filled with water up to the surface of thesoil. 3 days after sowing, the water level is increased to slightlyabove the soil surface (3-5 mm). Application is effected 3 days aftersowing by spraying the beakers with an aqueous emulsion of the testcompounds. The rate of application corresponds to a concentration of 4kg of active ingredient per hectare (concentration of the spraymixture=550 l/ha). The beakers are then kept in the greenhouse underoptimum growth conditions for rice weeds, i.e. at 25°-30° C. and at highhumidity. The evaluation of the tests takes place 3 weeks afterapplication.

Evaluation is made in accordance with the rating indicated in Example 9.

The results are given in Table 10:

                  TABLE 10                                                        ______________________________________                                        Compound   Echinochloa crus galli                                                                       Monocharia vag.                                     ______________________________________                                        5.01       2              1                                                   5.02       2              1                                                   5.03       3              1                                                   ______________________________________                                    

EXAMPLE 14 Growth inhibition of tropical leguminous cover crops

The test plants (Centrosema plumieri and Centrosema pubescens) arereared until fully grown and then cut back to a height of 60 cm. Theplants are sprayed 7 days later with an aqueous emulsion of the testcompound. The test plants are kept at 70% relative humidity and 6000 luxartificial light for 14 hours per day, at day temperatures of 27° C. andnight temperatures of 21° C. The test is evaluated 4 weeks afterapplication by assessing and weighing the new growth compared withcontrols and by determining the phytotoxicity.

In this test, a marked reduction in new growth of the plants treatedwith compounds of Tables 3 to 6 at concentrations of 50 to 3000 g/ha isobserved (less than 20% of the new growth of untreated control plants),without damage being caused to the test plants.

EXAMPLE 15 Growth regulation of soybeans

Soybeans of the "Hark" variety are sown in plastic containers in anearth/peat/sand mixture (6:3:1). The containers are put into a climaticchamber and the plants develop to the 5-6 trefoil leaf stage after abut5 weeks by optimum control of temperature, light, fertiliser addition,and watering. The plants are then sprayed with an aqueous mixture of acompound of Tables 3 to 6 until thoroughly wetted. The concentrationcorresponds to up to 100 g a.i. per hectare. Evaluation is made about 5weeks after application. Compared with untreated controls, the compoundsof Tables 3 to 6 of the invention markedly increase the number andweight of the harvested siliquae on the leading shoot.

EXAMPLE 16 Growth inhibition of cereals

Summer barley (Hordeum vulgare) and summer rye (Secale) are sown insterilised soil in plastic beakers in a greenhouse and watered asrequired. The cereal shoots are treated about 21 days after sowing withan aqueous spray mixture of a compound of Tables 3 to 6. Theconcentration corresponds to up to 100 g of active ingredient perhectare. Evaluation of the growth of the cereals is made 21 days afterapplication. A comparison with untreated controls shows that the growthof treated cereal plants is reduced (60-90% of the controls) and thatthe diameter of the stalks has in some cases increased.

EXAMPLE 17 Growth inhibition of grasses

Seeds of the grasses Lolium perenne, Poa pratensis, Festuca ovina,Dactylis glomerate and Cynodon dactylon are sown in plastic dishesfilled with an earth/peat/sand mixture (6:3:1), in a greenhouse, andwatered as required. The emergent grasses are cut back weekly to aheight of 4 cm, and about 50 days after sowing and 1 day after the lastcut are sprayed with an aqueous spray mixture of a compound of Tables 3to 9. The concentration of test compound corresponds to a rate ofapplication of up to 500 g a.i. per hectare. The growth of the grassesis evaluated 21 days after application. The test compounds of Tables 3to 6 effect a reduction in new growth in the range of 10-30% incomparison with untreated controls.

EXAMPLE 18 Desiccation and defoliation action

Cotton plants of the Delapine variety are reared in earthen-ware pots ina greenhouse. After the capsules have formed, the plants are sprayedwith an aqueous formulation of a compound of Tables 3 to 9 at rates ofapplication corresponding to 1.2, 0.6 and 0.3 kg/ha in fieldapplication. Untreated plants act as controls. Evaluation of the test ismade 3, 7 and 14 days after application of the active ingredient bydetermining the degree of defoliation (percentage of fallen leaves) andof desiccation (drying out of the leaves remaining on the plant).

In this test, plants treated with test compounds of Tables 3 to 6 atrates of application of 0.6 and 1.2 kg/ha are left after 7 days withonly a few dried out leaves (<80% defoliation and dessication).

What is claimed is:
 1. A pyridine compound of formula I ##STR25##wherein each of X, Y and Z independently of one another is hydrogen or aC₁ -C₄ alkyl group, or two adjacent substituents together also form asaturated or unsaturated 3- or 4-membered alkylene chain or alkenylenechain, each of which chains may in turn be substituted by one to four C₁-C₄ alkyl groups; R is the hydroxyamino group, a C₁ -C₄ alkoxyamino, C₃-C₄ alkenyloxyamino or C₃ -C₄ alkynyloxyamino group, a --PO(OC₁ -C₄alkyl)₂ or --PO(CH₃)OC₁ -C₄ alkyl radical or a hydrazino radical --NR₁NR₂ R₃, in which R₁ is hydrogen or C₁ -C₄ alkyl, R₂ is hydrogen, C₁ -C₄alkyl or benzyl and R₃ is hydrogen, C₁ -C₄ alkyl, benzoyl, carbamoyl,thiobenzoyl, thiocarbamoyl, C₁ -C₄ alkylcarbamoyl, di(C₁ -C₄alkyl)carbamoyl, C₁ -C₄ alkylthiocarbamoyl, di(C₁ -C₄alkyl)-thiocarbamoyl, anilido, thioanilido, C₁ -C₄ alkoxycarbonyl, C₁-C₄ alkylcarbonyl, C₁ -C₄ alkylthiocarbonyl or benzoyloxy, the phenylrings being unsubstituted or substituted by halogen, C₁ -C₄ alkyl, C₁-C₄ haloalkyl or C₁ -C₄ alkoxy, or R₃ is another3H-imidazo[1',2':1,2]pyrrolo[3,4-b]pyridine-2,5-dion-12-yl radical or athiazolylcarbamoyl radical.
 2. A compound according to claim 1, whereinR is the hydrazino radical, and X, Y and Z are as defined in claim
 1. 3.9b-Hydrazino-3,7-dimethyl-3-isopropyl-1H-imidazo[1',2':1,2]-pyrrolo[3,4-b]pyridine-2,5(3H,9bH)-dione according to claim
 1. 4. A compound according to claim 1,wherein R is the hydroxylamino radical, and X, Y and Z are as defined inclaim
 1. 5.9b-Hydroxylamino-3-isopropyl-3-methyl-1H-imidazo[1',2':1,2]pyrrolo[3,4-b]pyridine-2,5(3H,9bH)-dioneaccording to claim
 1. 6. A compound according to claim 1, wherein R is aC₁ -C₄ alkoxyamino or C₃ -C₄ alkenyloxyamino radical, and X, Y and Z areas defined in claim
 1. 7.3-Isopropyl-9b-methoxyamino-3-methyl-1H-imidazo[1',2':1,2]pyrrolo[3,4-b]pyridine-2,5(3H,9bH)-dioneaccording to claim
 1. 8.9b-Allyloxyamino-7-n-butyl-3-isopropyl-3-methyl-1H-imidazo[1',2':1,2]pyrrolo[3,4-b]pyridine-2,5(3H,9bH)-dioneaccording to claim
 1. 9.9b-Allyloxyamino-3-isopropyl-3-methyl-1H-imidazo[1',2':1,2]pyrrolo[3,4-b]pyridine-2,5(3H,9bH)-dioneaccording to claim
 1. 10.7-Ethyl-9b-allyloxyamino-3-isopropyl-3-methyl-1H-imidazo-[1',2':1,2]pyrrolo[3,4-b]pyridine-2,5(3H,9bH)-dioneaccording to claim
 1. 11. A method of controlling undesired plantgrowth, which method comprises the use of a herbicidally effectiveamount of a compound according to claim 1, or of a herbicidalcomposition containing such a compound.
 12. A method of inhibiting plantgrowth, which method comprises the use of an inhibiting affective amountof a compound according to claim 1, or of a herbicidal compositioncontaining such a compound.
 13. A method of influencing plant growth forincreasing the yield, which method comprises the use of a yieldincreasing effective amount of a compound according to claim 1, or of aherbicidal composition containing such a compound.
 14. A method ofselectively controlling weeds per- or postemergence in crops of usefulplants, which method comprises treating said useful plants or the cropareas thereof with a herbicidally effective amount of an imidazolinonecompound of formula I according to claim 1, or of a herbicidalcomposition containing such a compound.
 15. A method of suppressingplant growth beyond the 2-leaf stage, which method comprises treatingthe plants during their growth with growth surpressing effective amountof an imidazolinone compound of formula I according to claim 1, or of aherbicidal composition containing such a compound.
 16. A herbicidal andplant growth regulating composition which comprises, as activeingredient, a herbicidal effective amount of a compound according toclaim 1, together with a carrier or other adjuvants.